Quick Answer
Body fat percentage is commonly estimated using the U.S. Navy method, which calculates body density from waist, neck, and (for women) hip circumference measurements, combined with height.
What Is Body Fat %?
Body fat percentage represents the proportion of your total body weight that is made up of fat tissue, as opposed to lean mass (muscle, bone, organs, water). Unlike BMI, which only considers height and weight, body fat percentage gives a more direct picture of body composition, which is particularly useful for athletes, where BMI alone can be misleading due to high muscle mass.
The U.S. Navy method is one of the most widely used non-clinical estimation techniques, using simple tape-measure circumference measurements (neck, waist, and for women, hips) combined with height, run through a logarithmic formula. While not as precise as clinical methods like DEXA scans or hydrostatic weighing, it provides a reasonably consistent estimate that's accessible without special equipment.
Healthy body fat percentage ranges differ meaningfully by sex (women naturally carry more body fat than men at the same fitness level) and shift somewhat with age, making single 'ideal number' targets less useful than understanding the broader healthy range for your category.
How to Use
- 1Measure your neck circumference at its narrowest point, just below the larynx.
- 2Measure your waist circumference at the navel (for the standard method), for women, also measure hip circumference at the widest point.
- 3Enter your height, along with the measurements above and your sex.
- 4The calculator applies the U.S. Navy formula to estimate your body fat percentage.
Formula
BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387Example: Male, neck 38 cm, waist 85 cm, height 175 cm
- Using the men's formula with these measurements
- BF% = 86.010 × log₁₀(85−38) − 70.041 × log₁₀(175) + 36.76
Tips & Things to Know
- Measurement consistency matters significantly, measure at the same time of day, with the tape measure snug but not compressing the skin, for comparable results over time.
- The U.S. Navy method is an estimate, not a clinical-grade measurement, for precise body composition analysis (e.g. for medical or elite athletic purposes), DEXA scans or hydrostatic weighing are more accurate.
- Healthy body fat ranges differ by sex: roughly 10-20% is typical for fit men, and 18-28% for fit women, reflecting natural physiological differences, not a fitness deficiency.
- Tracking body fat percentage trend over weeks or months is generally more useful than any single measurement, since small measurement inconsistencies can shift a single reading.